The objective is to understand the relation between the sensory and association areas of the neocortex. Since the neocortex is the hallmark of man, the research proposed promises to reveal the neural basis for perception, learning and cognition. The proposal is to continue using the three shrew (Tupaia glis) as a model for higher primates. Earlier studies in this laboratory showed that the association visual cortex in Tupaia is the target of a sensory pathway originating in the tectum and relaying in the pulvinar nucleus. Tupaia provides a unique opportunity to learn more about the functional relation between th tecto-pulvinar and the geniculo-striate pathways because the behavioral deficits after ablation of either pathway alone is not incapacitating. Behavioral experiments are proposed to test acuity, pattern vision, and visual learning after ablation of the pulvinar nucleus or the striate cortex. Anatomical experiments are proposed to identify subdivisions of the pulvinar nucleus in Tupaia and their connections to cortex. Immunocytochemical and HRP transport studies are proposed to learn more about the projections of the reticular formation to the dorsal thalamus (and to the lateral geniculate and pulvinar nuclei, in particular). The use of antisera will identify terminals according to their neurotransmitter; serotonin, acetylcholine, and noradrenalin. Galago and Saimiri will be used in addition to Tupaia. Finally, it is proposed that the study of the laminar organization in striate cortex of lateral geniculate terminals be continued using the methods of intracellular injection and electron microscopy.